Some of the brightest objects in the Universe are supermassive black holes at the hearts of galaxies—black holes with masses millions or billions of times greater than the Sun. As matter falls toward these black holes, the system emits intense radiation, especially in the radio and X-ray portions of the electromagnetic spectrum. When light from the infalling matter reaches a maximum intensity, the systems are known as quasars, which are bright enough to shine out from the early Universe.

Stellar-mass black holes, which are "only" 5 to 20 times more massive than the Sun, can also produce intense light. However, interstellar gas absorbs and scatters the X-rays, making them difficult to spot. As a result, only four microquasars are known in the Milky Way, and we haven't been able to observe many details of them. No similar systems have been spotted in other galaxies—until now. Observers found the first microquasar in M31 (Andromeda Galaxy), the nearest large galaxy to the Milky Way.

Though black holes (either stellar-mass or supermassive) emit no light of their own, their intense gravity gathers matter around them. As charged particles such as electrons accelerate, they emit light; with the high acceleration rates around black holes, this light takes the form of X-rays and radio waves. (Even though X-rays are some of the highest energy radiation and radio waves are the lowest in energy, they are often produced by the same physical phenomena, and provide dual ways to observe some of the most violent events in the cosmos.)

The matter forms a rotating accretion disk around the black hole, and some is channeled into powerful jets streaming along the axis of rotation. The infalling particles in the disk interact with each other, so that pressure builds up within it. Eventually, it can build to the point where it pushes any additional matter away from the black hole. As a result, a black hole (or any other object) will reach a maximum brightness, known as the Eddington luminosity, named for the astronomer Arthur Eddington. Quasars are supermassive black holes shining at or near the Eddington luminosity, and microquasars are likely stellar-mass black holes whose accretion is similarly close to the theoretical maximum.

The orbiting XMM-Newton X-ray observatory discovered XMMU J004243.6+412519, a bright X-ray source in M31 in January 2012. Later, the object flared to a peak luminosity greater than 1032 Watts. For reference, the Sun's luminosity is 3.8×1026 Watts, including all types of light. In other words, this object emits roughly a million times the energy of our Sun in X-rays alone. If that wasn't enough, this particular microquasar was 10 times brighter than any other known object in M31.

Astronomers monitored the ultraluminous X-ray source (ULX) using the Swift and Chandra orbiting observatories for X-rays, along with the Jansky Very Large Array (VLA) in New Mexico, the Very Long Baseline Array (VLBA), and the Arcminute Microkelvin Imager Large Array (AMI-LA) for radio light. These observations allowed the researchers to rule out the possibility that the microquasar was actually a more distant background object peeking through M31's disk. They also were able to determine that the emission from the ULX varied on a rapid timescale (varying measurably over tens of minutes for X-ray, and over a few days for radio). This variation is a hallmark of accretion, since matter doesn't fall inwards in a steady stream.

Unlike microquasars in the Milky Way, those in other galaxies potentially provide an unimpeded view of the black hole accretion process. This will allow astronomers to test whether microquasars are miniature versions of their supermassive cousins, and measure the accretion mechanism in unprecedented detail. Since the nearest "regular" quasars are much farther away than M31, a nearby microquasar provides a beautiful target for observations of how black holes beam infalling matter into jets, and the specific processes are by which they make their intense light.

The authors of the present study even postulated that, thanks what they've learned through this discovery, they will be able to locate other microquasars using radio emissions. If true, this would be more efficient and faster than X-ray based searches, not to mention higher resolution: the VLA and VLBA both provide pinpoint locations for bright sources. This M31 microquasar could be the first of many discovered in other galaxies, providing understanding of how many there are, and how they may influence their environment.

As charged particles such as electrons accelerate, they emit light; with the high acceleration rates around black holes, this light takes the form of X-rays and radio waves. (Even though X-rays are some of the highest energy radiation and radio waves are the lowest in energy, they are often produced by the same physical phenomena, and provide dual ways to observe some of the most violent events in the cosmos.)

Can someone kindly point me towards a explanation to why light emitted by accelerating electrons "skips" the light wave lengths in between radio and x-rays? Thanks.

Cool -- thanks! Though it's hard for me to think about radio waves from Compton without getting NWA stuck in my head.

See above; I initially wrote it backwards. It gets confusing, because most power is emitted in x rays by synchrotron radiation, but most photons are radio. I have to think about it carefully to remember.

Later, the object flared to a peak luminosity greater than 10e32 Watts. For reference, the Sun's luminosity is 3.8×10e26 Watts, including all types of light. In other words, this object emits roughly a million times the energy of our Sun in X-rays alone. If that wasn't enough, this particular microquasar was 10 times brighter than any other known object in M31.

So, that makes the object 2.63×10e5 times as "bright" as the Sun. To appear equally bright, it would need to be about 513 times the distance, or 0.008 light-years away. That means that I don't have to worry too much about one passing by and sterilizing the Earth anytime soon.

Can someone kindly point me towards a explanation to why light emitted by accelerating electrons "skips" the light wave lengths in between radio and x-rays? Thanks.

The x rays are from synchrotron and black body emissions, the "primary radiation" if you will. The radio waves are from Compton scattering.

Cool -- thanks! Though it's hard for me to think about radio waves from Compton without getting NWA stuck in my head -- "Crazy mother-f'er named Electron".

Nope, you had correct the first time. Radio wavelengths are created via synchrotron radiation. The X-ray wavelengths are created via bremsstrahlung (electron free-free) interaction. There is evidences in accretion disk dynamics that suggest thermal UV radiation created by frictional heating of the accretion disk is up scattered via inverse Compton scattering (UV photon is boosted into X-ray energies by an encounter with a relativistic electron). We have evidence that this happens although to what extent is current debated in scientific literature.

Nope, you had correct the first time. Radio wavelengths are created via synchrotron radiation. The X-ray wavelengths are created via bremsstrahlung (electron free-free) interaction.

Right. I wrote the opposite of this at first, and fixed it. Radio = direct synchrotron = electron accelerating in magnetic field, x-ray = inverse Compton = radio photon that collided with a relativistic electron.

'Some of the brightest objects in the Universe are supermassive black holes at the hearts of galaxies—black holes with masses millions or billions of times greater than the Sun. 'I love it when theory becomes fact just because, well, it's been talked to death and never proven.

'I love it when theory becomes fact just because, well, it's been talked to death and never proven.

It has been tested to death and not talked to death. The difference is huge.And if no other explanations offer an explanation, you may just as well skip the "it is believed" every time you mention it. I am sure one of the real scientists on the site can express this a lot better.

But feel free to offer another explanation for Extremely bright (but not in visible spectrum, hence not a star), super-massive - (millions of suns mass - inferred from their small size and the orbits of nearby suns) objects in the center of some galaxies.

"'Some of the brightest objects in the Universe are supermassive black holes at the hearts of galaxies—black holes with masses millions or billions of times greater than the Sun. 'I love it when theory becomes fact just because, well, it's been talked to death and never proven."

That passage contains basically nothing but facts. The objects are measurably brighter than anything else, they are measurably millions even billions of times more massive than our Sun.

Now if you want to discuss whether the hypothesis about the nature of 'black holes' are the most ideal given those facts thats a complex issue with many different facets and a fair bit of ongoing research but to say this much isnt proven is nonsense its been recorded by every decent observatory on Earth.

(Incidentally, theories are never facts regardless of the quantity of proof. Theory is as good as science can ever get which is why people will consider many theories in a matter of fact manner.)

'I love it when theory becomes fact just because, well, it's been talked to death and never proven.

It has been tested to death and not talked to death. The difference is huge.And if no other explanations offer an explanation, you may just as well skip the "it is believed" every time you mention it. I am sure one of the real scientists on the site can express this a lot better.

But feel free to offer another explanation for Extremely bright (but not in visible spectrum, hence not a star), super-massive - (millions of suns mass - inferred from their small size and the orbits of nearby suns) objects in the center of some galaxies.

How about 'we still don't know shit' what's going on'. They can't even explain what's going on inside the sun, and I should take for granted their theories about the center of the galaxy. Yea right.

"'Some of the brightest objects in the Universe are supermassive black holes at the hearts of galaxies—black holes with masses millions or billions of times greater than the Sun. 'I love it when theory becomes fact just because, well, it's been talked to death and never proven."

That passage contains basically nothing but facts. The objects are measurably brighter than anything else, they are measurably millions even billions of times more massive than our Sun.

Now if you want to discuss whether the hypothesis about the nature of 'black holes' are the most ideal given those facts thats a complex issue with many different facets and a fair bit of ongoing research but to say this much isnt proven is nonsense its been recorded by every decent observatory on Earth.

(Incidentally, theories are never facts regardless of the quantity of proof. Theory is as good as science can ever get which is why people will consider many theories in a matter of fact manner.)

Excuse you, black holes are still theory, so is the whole Big Bang crap.

'Excuse you, black holes are still theory, so is the whole Big Bang crap.'

Kind of going over your head... The passage you quoted spoke about the mass, which is confirmed fact. The brightness, which is confirmed fact. and mentioned the name 'black holes' which is what we call the massive gravitational force at the heart of these effects so is accurate. Black holes are indeed a theory. (In fact much of the black hole model is still hypothesis, some even just speculation.)

There is nothing better than theory, no science ever gets beyond it. Black holes are still theory, gravity is still theory, thermodynamics is still theory. Its all theory, it can all change the moment someone finds something better, thats how science works.

You cant just say this is all nonsense because every issue hasnt been dealt with, youd end up considering _everything_ to be nonsense because _everything_ has an issue at some point because _everything_ is a theory. You can list the facts and say what the experts believe is going on which is exactly what the article did.

If you have an issue with this then you probably shouldnt read another scientific article or paper ever again because thats all any of them ever do, will ever do and can ever do.

At the beginning, the article equates super massive black holes with quasars, but then at the end says:

".. Since the nearest "regular" quasars are much farther away than M31..."

So, the Milky Way's black hole is not a quasar, nor is the one at the center of Andromeda. Why isn't ours a quasar? This part is unclear.

"When light from the infalling matter reaches a maximum intensity, the systems are known as quasars..."

Our black hole does not achieve the maximum accretion rate possible.

Pff, crappy, underperforming black hole.

. o O (I do hope this will help shed some more light on the process responsible for the jets. (I think the jets themselves shed rather enough light to read by.))

I was under the impression that a quasar is a relativistic jet from a supermassive black hole that happens to be pointed towards us. Now I can't remember if that was wild speculation, science fiction, or accepted theory.

Etek, if you think it's bullshit, why even bother reading/commenting on the article? Your ignorance is exemplified by the sentence you originally called out, since, as rcb2603 explained, the mass and brightness are observable, so your only real objection is to calling it a black hole? The general "idea" of a black hole?

The current theories are built on observations and past theories that have shown to be robust (e.g. relativity) and are yet to be disproven, though I'm sure theories will continue to be refined and changed based on observation as refining these theories is a gradual process. Please take some time to learn about the scientific method, and if you wish to continue to be willfully ignorant then please stay out of these discussions.

These are some of my favorite articles on the site, i'd hate for anti-science trolls to take over this little haven on the net as well.

So, that makes the object 2.63×10e5 times as "bright" as the Sun. To appear equally bright, it would need to be about 513 times the distance, or 0.008 light-years away. That means that I don't have to worry too much about one passing by and sterilizing the Earth anytime soon.

I'll still remain paranoid about gamma-ray-bursts pointing in our direction. Those death-rays only need to be within 100,000ly to kill us.

As charged particles such as electrons accelerate, they emit light; with the high acceleration rates around black holes, this light takes the form of X-rays and radio waves. (Even though X-rays are some of the highest energy radiation and radio waves are the lowest in energy, they are often produced by the same physical phenomena, and provide dual ways to observe some of the most violent events in the cosmos.)

Can someone kindly point me towards a explanation to why light emitted by accelerating electrons "skips" the light wave lengths in between radio and x-rays? Thanks.

I have no idea, but I'll take a random guess.

An electron having almost no mass in an extremely strong magnetic field is probably almost always at relativistic speeds. The chance of a radio wave hitting a slow enough electron to emit visible light is probably very slim.

A curiosity I've always had: Quasars have always puzzled me because we're all taught that the gravitational field of a black hole warps space so much that that not even light can escape it. So... I've always wondered how these jets manage to do so. Do they emanate somehow from the accretion disk before the matter crosses the event horizon, or do they erupt internally from within the black hole itself?

If they come from within the black hole itself, isn't it then a misnomer that nothing can escape the gravitational force of a black hole? IIRC the quasar's jets originate from the magnetic poles, so I'm guessing the magnetic field of the black hole is weaker at the poles, as it is on Earth, which allows the matter/energy to escape. Perhaps the event horizon itself is not a uniform spheroid around the black hole as I would imagine a gravitational field to be, but instead shaped to match that of the magnetic field?

Wouldn't that mean that it's not the gravity then that's hard to escape from a black hole, but it's magnetism?

Makes me wonder at the likelihood then that gravity is not actually how a body warps space/time around it, but that gravity is really more of the sum quantum magnetic attraction between bodies.

Another possibility being that if gravity can be strong enough to warm space/time then why not magnetism and the gravitational field around a black hole is normal (non-space/time warping), but it's the magnetic field that does all the warping preventing light's escape.

.. Do [jets] emanate somehow from the accretion disk before the matter crosses the event horizon, or do they erupt internally from within the black hole itself? ...

Both, in a way. The mass itself never crossed the event horizon, but was captured in the ergosphere; the equatorial bulge around the rotating center, where space is being dragged around faster than light itself.

Material that falls into this region, but avoids the event horizon for whatever reason (like coming in fast at a shallow angle), pulls momentum from the rotation of the black hole through frame dragging as it passes, and then exits with far more energy than it had.

That energy was pulled from "inside" the black hole, but the particles themselves were not black hole natives.

How exactly that gets spiraled out along the poles, and not just shot off into space; I'm still wrapping my head around.